For example, as display apparatuses using three primary colors such as R (red), G (green), and B (blue), LED displays using light-emitting diodes (LEDs) have been developed. The LED displays have high luminance and high color purity. The LED displays utilizing characteristics of an LED light source as a point light source are frequently used as indoor and outdoor large displays. Most of the LED displays make it possible to form a seamless large display by combining and arranging some independent modules (by so-called tiling).
In the LEDs, variation in wavelength or color purity occurs due to variation during manufacturing. Typically, most of red LEDs are made of an AlGaInP-based compound semiconductor crystal, and most of blue and green LEDs are made of an AlGaInN-based compound semiconductor crystal. There are various causes of the wavelength variation such as the crystal orientation, composition, thickness, and arrangement of a mixed crystal during crystal growth, and processing accuracy. Since nonuniformity is easily increased in an AlGaInN-based mixed crystal, the wavelength variation easily occurs specifically in the blue and green LEDs.
When LEDs that vary in wavelength and chromaticity are provided in respective pixels, it may be difficult to match colors of the respective pixels, thereby causing degradation in image quality such as rough display, the occurrence of color unevenness in a display screen, a difference in color between tiled units, and difficulty in displaying an exact color.
Accordingly, there is disclosed a technology for measuring variation (characteristics) in wavelengths of respective LEDs of R, G, and B between pixels to correct luminance and chromaticity (for example, refer to PTL 1).